Author(s)

Sergey A. Menzikov^*, Margarita N. Karpova, Lada V. Kuznetsova, Natalya Y. Klishina

Federal State Scientific Institution “Research Institute of General Pathology and Pathophysiology”, Moscow, Russia.

This work examines the influence of Cl^- (2.5 - 125 mM) and HCO₃^- (2 - 30 mM) on the Cl^-/HCO₃^- - ATPase complex of the neuronal membrane and this enzyme is a Cl^--pump that is coupled to GABA_A receptors. The greatest (44%) activating effect on the enzyme is found with HCO₃^- (20 - 30 mM), while the maximum activity occurs in the presence of a ratio of ~25 mM HCO₃^- /~5mM Cl^-. Blockers of the GABA_A receptor, namely bicuculline (10 - 50 μM) and picrotoxin (50 - 100 μM), inhibit this anion activation, whereas the HCO₃^- -ATPase activity is not sensitive to these ligands. Autoradiographic analysis of the spectrum of the partially purified enzyme phosphorylated with [γ^-32P]ATP allowed us to distinguish three major ³²P-labeled protein whose molecular weight are about 57, 53, and 48 kDa. In the presence of 5 mM Cl^-/25mM HCO₃^- and 100 μM picrotoxin, the intensity of the phosphorylation of bands significantly decreased, thereby confirming the assumption about coupled of binding sites for anions and GABA_A-ergic ligands. It was suggested scheme of Cl^--transport through the plasma membrane by utilizing neuronal Cl^-/ -HCO₃^- ATPase in the low (5 mM) Cl^- and high (25 mM) HCO₃^- concentrations. The data demonstrated for the first time that the GABA_A-coupled Cl^-/ HCO₃^- -ATPase from rat brain neuronal membranes is maximally activated at a Cl^-/HCO₃^- ratio of 1:5 and it remains stable at high concentrations of substrate and buffer.

Rat Brain, Plasma Membrane, Mg2+-ATPase, Chloride, Bicarbonate, Mg2+-ATP, Picrotoxin, Bicuculline, Autoradiography, Molecular Weight, Subunits

Menzikov, S. , Karpova, M. , Kuznetsova, L. and Klishina, N. (2015) GABA_A-Coupled Cl-/ HCO₃^--ATPase from Plasma Membrane of the Rat Brain: Role of HCO₃^- in the Enzyme Activation. Advances in Enzyme Research, 3, 9-18. doi: 10.4236/aer.2015.31002.